1. Field of the Invention
The present invention relates to a radio communications method for set up a connection between a radio network controller and a mobile station located in a specific cell under control of the radio network controller, and a radio network controller used in the radio communications method.
2. Description of the Related Art
Conventionally, a radio communications system using a W-CDMA (Wideband-Code Division Multiple Access) scheme, that is to say, a radio communications system for set up a connection between a radio network controller and a mobile station located in a specific cell under control of the radio network controller is known.
As shown in FIG. 1, the radio communications system using the W-CDMA scheme is configured with a core network CN, a radio network controller RNC, node-Bs, and mobile stations UEs (User Equipments).
In fact, there are a plurality of radio network controllers RNCs, a plurality of node-Bs, and a plurality of mobile stations UEs. However, in order to simplify an explanation, FIG. 1 shows one radio network controller RNC, two node-Bs #1 and #2, and two mobile stations UE#1 and UE#2.
In the radio communications system using the W-CDMA scheme, a radio access network RAN (UTRAN) is configured with the radio network controller RNC and the node-Bs.
The radio network controller RNC is connected to the core network CN via an Iu interface. The radio network controller RNC is configured to perform management of radio resources, control of node-Bs and the like. For example, the radio network controller RNC performs control of a hand-over process.
The node-B is connected to the radio network controller RNC via a Iub interface. To be more specific, the node-B is configured with a base station which controls one or more cell(s).
When the node-B divides the cells into a plurality of sectors by using a plurality of directional antennas, so as to control the sectors, each sector is called a “cell” in the embodiment.
In FIG. 1, the node-B #1 controls a cell #1, and the node-B #2 controls a cell #2.
The mobile station US is configured to be connected to the node-B and the radio network controller RNC via a radio interface.
A protocol architecture of the radio interface in the radio communications system using the W-CDMA scheme consists of a protocol layer including a physical layer (a layer 1), a data link layer (a layer 2), and a network layer (a layer 3).
The layer 2 is divided into a MAC (Media Access Control) sub-layer and a RLC (Radio Link Control) sub-layer.
An RRC (Radio Resource Control) which belongs among the layer 3 has a function of providing various services with an upper layer. The various services include a notification of broadcast information to all mobile stations UEs located in cells which the radio network controller RNC controls, a call of a specific mobile station by the radio network controller RNC (transmission of paging), and setup/change/release of an RRC connection between the radio network controller RNC and the mobile station UE.
As shown in FIG. 2, a state of the mobile station UE changes from an Idle mode to a Connected mode (an RRC connected state), when a connection is established between the mobile station UE and the radio network controller RNC.
On the other hand, the state of the mobile station UE changes from the Connected mode to the Idle mode, when the connection is released between the mobile station UE and the radio network controller RNC.
FIG. 3 shows a sequence of when the state of the mobile station UE changes from an Idle mode to a Connected mode in the conventional radio communications system for providing an MBMS (Multimedia Broadcast Multicast Service).
As shown in FIG. 3, in step 101, the mobile station UE #1 is working in the Idle mode. That is, the mobile station UE #1 is working in the state where an RRC connection is not set up between the mobile station UE #1 and the radio network controller RNC.
In step 102, the core network CN transmits a paging for calling the mobile station UE #1 to the radio network controller RNC.
In step 103, the radio network controller RNC transfers the received paging to the mobile station UE #1 via the node-B #1.
In step 104, the mobile station UE #1 performs an RRC connection setup procedure for setting up an RRC connection between the mobile station UE #1 and the radio network controller RNC by transmitting an RRC connection request to the radio network controller RNC, when the paging received by the mobile station UE #1 is directed to the mobile station UE #1.
In step 105, the state of the mobile station UE #1 changes for the Idle mode to the Connected mode.
However, in the conventional radio communications system using the W-CDMA scheme, the radio network controller RNC is configured to manage information (the number, the reception capability and the like) of mobile stations UEs of Connected mode located in specific cells which the radio network controller RNC, the core network CN is configured to manage the information of mobile stations UEs of Idle mode located in the specific cells.
Therefore, there is a problem in that the radio network controller RNC can not grasp movement of the mobile stations UEs of the Idle mode in cells under control of the radio network controller RNC, so as not to accurately manage the information of the mobile stations UEs located in the cells.